Thorax:Arterial structure:Subclavian arteries
The subclavian arteries are asymmetric paired arteries that supply blood to the posterior cerebral circulation, cerebellum, posterior neck, upper limbs and the superior and anterior chest wall. Origin Right and left subclavian arteries classically have different origins: * right subclavian artery (RSA) is one of the terminal branches of the brachiocephalic artery * left subclavian artery (LSA) arises as the third branch of the aortic arch after the left common carotid artery Course The subclavian artery exits via the thorax via the superior thoracic aperture between the anterior and middle scalene muscles before passing between the first rib andclavicle. At the lateral border of the first rib it continues as the axillary artery. The vessel can be split into three parts (first, second, third) depending on the position of the vessel in relation to scalenus anterior: * first part: from its origin to the medial border of scalenus anterior. It arches over the suprapleural membrane and leaves a groove on the lung apex. * second part: posterior to scalenus anterior * third part: from the lateral border of scalenus anterior to the lateral border of the first rib Differences of left and right subclavian: * right subclavian arise from brachiocephalic trunk, behind SC. It is crossed by the right IJV and vertebral vein, right vagus, which gives the recurrent laryngeal that loops the artery. Posteriorly related to the pleura and apex of the lung. * left subclavian arise from the aorta, behind the left carotid at T4. Anteriorly related to vagus, phrenic, left IJV and vertebral vein. Posteriorly related to the oesophagus, thoracic duct, left recurrent laryngeal nerve. Branches * first part: ** vertebral artery: courses cranially to the foramen of the transverse process of C6, occasionally C5. A coonnecting loop between middle and inferior cervical ganglia passes in front of the subclavian artery forming the ansa subclavia. ** internal thoracic artery: courses caudally over the lung apex and crossed anteriorly by phrenic nerve. ** thyrocervical trunk: very short trunk that arise lateral to vertebral artery and divides into superficial cervical, suprascapular and inferior thyroid arteries. * second part ** costocervical trunk: courses cranially before bifurcation into superior intercostal artery and deep cervical artery. * third part ** dorsal scapular artery: courses posteriorly and through the brachial pelxus in front of scalenus medius and deep to the levator scapulae to join to scapular anastomosis. Variant anatomy The subclavian vessels may arise from aberrant locations if there is failure of the normal embryological aortic arch development. * Aberrant right subclavian artery: can arise from different position, 1st to 5th of the arch ** 1st branch: replaces the brachiocephalic trunk ** 2nd - 4th: runs behind the right common carotid ** 5th branch: distal to the left subclavian artery and courses posteriorly between the trachea and oesophagus (retrotracheal) or behind oesophagus (retro-oesophageal) where it may cause compression resulting in breathing difficulties or dysphagia. * Right sided aortic arch with left subclavian passing retro-oesphageal * Various division of the brachiocephalic: high vs low * Thoracic aorta origin of left subclavian * Perforation of scalene anterior muscle